Field of the Invention
The present invention relates to a device for closing a closure member hinged on a support, which closing device comprises an actuator mechanism having a resilient member which is arranged to urge the hinged closure member towards its closed position and a hydraulic damper mechanism for damping the closing movement of said hinged closure member under the action of said resilient member.
Background
The actuator mechanism comprises a frame, a reciprocating pushrod which is slidably mounted on said frame to translate between an extended and a retracted position when opening and closing the hinged member, and the resilient member which is arranged between said pushrod and said frame to urge the pushrod towards its extended position. The hydraulic damper mechanism comprises a cylinder barrel defining a closed cylinder cavity, a reciprocating piston placed within said cylinder barrel so as to divide the cylinder cavity into a first side and a second side, a first motion converting mechanism for converting the translational motion of said pushrod into a rotational motion of a first pinion, which first motion converting mechanism comprises a first rack and pinion gearing having a first rack on said pushrod which engages said first pinion, a transmission, including a second motion converting mechanism, between said first pinion and said piston for transmitting and converting the rotational motion of said first pinion into a translational motion of the piston, a one-way valve allowing fluid flow from said first side to said second side of the cylinder cavity when opening the hinged member, and at least one restricted fluid passage between said first and second sides of the cylinder cavity.
Such a closing device, which shows all of the features of the preamble of claim 1, is disclosed in WO 2011/023793 and is offered for sale by the applicant under the name Samson. The Samson closing device or gate closer is intended for outdoor use, more particularly for closing gates or doors, such as garden or industrial gates or doors. The closing device is hingedly mounted, on the one hand, on the closure member and, on the other hand, on the support of the closure member so that when opening the closure member the pushrod of the closing device is pushed in and the resilient member, which is formed by a compression spring, compressed whilst when the closure member is released it is automatically closed by the pushrod which is pushed out again by the relaxing compression spring.
A problem with closing devices which are mounted in such a way is that the distance over which the pushrod is pushed in when opening the closure member over for example 90° dependents on the position of the hinge axis of the hinged closure member with respect to the position of the hinge axis of the closing device on the support. These positions may vary for example as a result of the diameter or thickness of the support and also as a result of the type of hinge, i.e. whether the hinge axis is situated between the support and the hinge member, for example for so-called 90° hinges, or whether the hinge axis is situated at a distance in front of the support and the hinged member, for example for so-called 180° hinges. The position of the different hinge axes also depends of course on the relative positions wherein the hinged closure member and the closing device are mounted on the support.
To ensure a correct functioning of the closing device in a broad range of different situations, the maximum stroke of the pushrod should be quite large and is for the prior art Samson gate closer equal to about 140 mm. An advantage of such a large stroke is that a quite long but relatively weak resilient member can be used, i.e. a resilient member with a relatively low spring constant, so that a smaller force needs to be exerted onto the resilient member to store a same amount of energy therein. In other words, less stresses are exerted onto the components of the closing device and on the connections thereof with the hinged member and with the support.
In the Samson gate closer, the pushrod has a toothed rack which co-operates with a pinion provided on the rotary damper shaft. The hydraulic damper mechanism comprises a screw-threaded piston/piston rod motion converting mechanism in which the damper shaft is screwed into the piston so that the rotational motion of the pinion is converted into a translational motion of the piston. When the pushrod is pushed in maximally, i.e. over a distance of 140 mm, the piston moves over a distance of about 47 mm and displaces about 112 ml of hydraulic liquid since the piston has a diameter of 55 mm. When the door or gate is being closed, part of this hydraulic liquid flows through the clearance between the piston and the cylinder whilst another part of the hydraulic liquid flows through a restricted fluid passage which is provided with an adjustable needle valve. In the example described in WO 2011/023793, the diameter of the cylinder is, at 20° C., 0.03 mm larger than the diameter of the piston so that, at this temperature, the clearance between the piston and the cylinder has a surface area of 2.6 mm2. By the use of a synthetic material for the piston, which has a larger thermal expansion coefficient than the aluminium of the cylinder, the surface area of the clearance between the piston and the cylinder becomes smaller as the temperature increases and becomes larger as the temperature decreases thus compensating for the change of the viscosity of the hydraulic liquid as a result of a change of the temperature.
A drawback of this prior art closing device is that the piston of the hydraulic damper mechanism moves up and down in the cylinder barrel so that this cylinder barrel has to project over a relatively large distance underneath the actuator mechanism. The lead of the screw thread on the damper shaft, which has four starts, has moreover to be quite large, and is equal to about 30 mm, so that due to the play between the co-operating threads, which has also to be relatively large to reduce the friction, the closing movement of the closure member is not immediately damped. When releasing the closure member, it is therefore closed initially at a higher speed until the screw thread on the damper shaft suddenly engages the screw thread on the piston again so that the closing movement is suddenly slowed down and the piston starts to be moved in the opposite direction to damp the closing movement. The transition between the opening and the closing movement is thus not smooth as the initially undamped movement is suddenly damped when the screw thread on the damper shaft engages the screw thread on the piston. A final important drawback is that, notwithstanding the relatively large play between the screw thread on the damper shaft and the screw thread on the piston, quite a lot of energy is lost by frictional forces between the screw threads on the piston and on the damper shaft. The spring constant of the compression spring has thus to be higher so that larger forces need to be exerted onto the closure member to open it and larger stresses arise in the closing device.
Other prior art closing devices with a hydraulic damper and with a pushrod comprise a horizontal hydraulic cylinder wherein the pushrod is formed by the piston rod which slides in and out of the hydraulic cylinder. Such a closing device is for example disclosed in U.S. Pat. No. 3,057,004. A drawback of these closing devices is that hydraulic liquid is lost through the sliding seal between the piston rod and the cylinder barrel. Although this loss may be quite limited, the closing device is not maintenance free which is an important disadvantage. Moreover, a tight sliding seal causes additional frictional losses. The piston itself is also provided with an elastic seal, which increases the frictional forces between the piston and the cylinder.
To avoid oil losses, U.S. Pat. No. 3,028,620 discloses a hydraulic damper which comprises two horizontal cylinders, one on top of the other. The uppermost cylinder receives the pushrod whilst the lowermost cylinder houses the piston and the piston rod. The pushrod is connected to the piston rod through a slit connecting the upper to the lower cylinder cavity. Only the lower cylinder cavity is filled with hydraulic liquid. A drawback of such a hydraulic damper is that a long hydraulic cylinder has to be provided since not only the piston but also the piston rod has to reciprocate within the hydraulic cylinder. The closing device is therefore also quite voluminous. Moreover, an elastic seal is provided between the piston and the cylinder wall which increases the frictional forces between the piston and the cylinder. Due to the presence of this elastic seal, a compensation of a varying viscosity of the hydraulic liquid by the use of a piston with a higher thermal expansion coefficient than the cylinder, as disclosed in WO 2011/023793, can therefore not be applied. Even without an elastic seal around the piston, this would still not be possible since the diameter of the piston is too small to achieve a sufficiently large change of the width of the clearance between the piston and the cylinder wall upon a change of the temperature to be able to compensate for the change in viscosity of the hydraulic liquid. Providing a clearance which is considerably smaller than the clearances disclosed in WO 2011/023793 in order to increase the relative effect of the temperature on the width of this clearance is not feasible is practice, especially not for long cylinder cavities such as in the hydraulic dampers disclosed in U.S. Pat. No. 3,057,004 and U.S. Pat. No. 3,028,620. Moreover, when providing only a very small clearance between the piston and the cylinder wall, only a very small part of the hydraulic liquid would be able to flow through such a clearance so that any change thereof would almost not affect the total flow of liquid. Nearly all of the hydraulic liquid would indeed flow through the restricted passage instead of through the clearance between the piston and the cylinder wall.
Another type of hydraulically damped door closers comprises the door closers which don't have a pushrod but which have instead a rotating arm. The rotating arm is mounted on a vertical shaft which carries a pinion. A rack on the piston rod co-operates with this pinion so that the piston reciprocates in the cylinder cavity. The door closer is mounted with the hydraulic cylinder in a horizontal position. An example of such a door closer is disclosed in EP 1 959 081. A drawback of such door closers is that either the horizontal hydraulic cylinder or the rotating arm is to be mounted above the door onto the door frame. Such door closers thus require a door frame above the door and can therefore not be used for doors or gates which have no frame on top of the door or gate. Generally, this is the case for outdoor applications, for example for garden gates. When applying such a door closer for garden gates without a frame, a projecting arm has to be mounted on the front side of the support so that the door closer can be mounted between this arm and the hinged member. A drawback thereof is that this projecting arm can be dangerous for a person approaching the gate whilst also the rotating arm can be dangerous since it forms a scissor mechanism that can cut or trap fingers, especially when it is situated on a relatively low level which is often the case with garden gates.
Another type of gate closer which comprises a rotating arm and which is offered for sale by the applicant under the name Verticlose is disclosed in WO 2011/023793. Just like the Samson gate closer disclosed in this international patent publication, the damper shaft is screwed into the piston so that the rotational motion of this damper shaft is converted into a translational motion of the piston. In this way, the hydraulic cylinder can be mounted vertically instead of horizontally. The rotary gate closer shows however the same disadvantages as to friction and lack of a smooth operation as described hereabove for the Samson gate closer comprising the same screw-threaded piston/piston rod motion converting mechanism. Moreover, a torsion spring has to be used which increases the height of the closing device even more and which is less appropriate for closing larger or heavier gates.
An object of the present invention is now to provide a new closing device which has a hydraulic damper mechanism and an actuator mechanism with a pushrod and a resilient member but which does not show the above-described disadvantages of a damper with a screw-threaded piston/piston rod motion converting mechanism and which does not show the friction losses caused by the presence of an elastic seal on the piston and the oil leakage which always occurs when use is made of a piston rod which slides horizontally in and out of the hydraulic cylinder.